Severe Storms Possible Today

[NWIASpotter]

The Storm Prediction Center has listed 3 areas in a slight risk. The first is areas of the upper ms valley (Northern Iowa, Eastern Minnesota, Western Wisconsin). The second area is portions of NE, KS, OK, TX, CO, NM. The last area is portion of the OH valley (OH, IN, PA, KY). None of these areas are particularly strong, only probabilities of 15% at most. But the threat does exist.

...SYNOPSIS...
WELL-DEFINED MIDDLE-UPPER SYNOPTIC PATTERN WILL CHARACTERIZE DAY-1. TROUGH WILL PERSIST FROM NWRN ONT TO LOWER RIO GRANDE VALLEY...WEAKENING FROM MKC AREA SWD AS HEIGHTS RISE BETWEEN ATLANTIC COAST AND 4-CORNERS HIGHS. NW FLOW OVER CENTRAL ROCKIES AND ADJACENT HIGH PLAINS Is EXPECTED TO STRENGTHEN AS HEIGHT GRADIENTS TIGHTEN WITH INTENSIFICATION OF 4-CORNERS ANTICYCLONE. SHORTWAVE TROUGH PRESENTLY EVIDENT ON MOISTURE CHANNEL IMAGERY OVER DAKOTAS/NRN NEB IS FCST TO MOVE EWD TO UPPER MS VALLEY REGION BY END OF PERIOD.

AT SFC...WEAK CYCLONE ANALYZED OVER SWRN MN/EXTREME ERN SD AREA WILL MOVE EWD TOWARD WRN WI...WITH TRAILING TROUGH AND WEAK FRONT MOVING EWD AND SEWD ACROSS PORTIONS CENTRAL/ERN NEB. MCS HAS DISSIPATED WITHIN PAST 2-3 HOURS OVER SERN NEB/NERN KS. THIS SYSTEM HAS LEFT WELL-DEFINED OUTFLOW BOUNDARY FROM E-CENTRAL CO...VICINITY LIC...SEWD ACROSS SWRN KS TO DDC/GCK AREA.

...CENTRAL HIGH PLAINS...
WIDELY SCATTERED TSTMS ARE FCST TO DEVELOP THIS AFTERNOON IN INCREASINGLY UNSTABLE AND RELATIVELY WEAKLY CAPPED AIR MASS. ELY/UPSLOPE FLOW COMPONENT WILL CONTRIBUTE TO LOW LEVEL ASCENT AND MOIST ADVECTION IN PRE-STORM AIR MASS...AND ONCE CONVECTION Is UNDERWAY...TO VERTICAL SHEAR AND STORM-RELATIVE INFLOW SUPPORTING POTENTIAL FOR A FEW SUPERCELLS. STRONG DIABATIC HEATING/MIXING WILL LEAD TO HIGH CLOUD BASES RELATIVE TO CONVECTION FROM YESTERDAY...BUT STILL WILL SUPPORT POTENTIAL FOR LARGE HAIL AND DAMAGING GUSTS. MODIFIED RAOBS AND RUC/ETA SOUNDINGS SUGGEST 1000-1500 J/KG MLCAPE IS POSSIBLE IN AN ENVIRONMENT OF 150-300 J/KG 0-3 KM SRH. ACTIVITY
MAY ORGANIZE INTO TSTM COMPLEX AFTER DARK WITH SEWD TO SSEWD NET MOTION TOWARD WRN KS...SERN CO AND PERHAPS OK/TX PANHANDLES. POTENTIAL EXISTS FOR A COLLECTIVE COLD POOL AND FORWARD PROPAGATION...WITH DAMAGING GUSTS BEING MAIN THREAT.

...OH VALLEY/GREAT LAKES...
TSTM COVERAGE IS FCST TO INCREASE OVER THIS AREA FROM LATE MORNING THROUGH EARLY EVENING. DIABATIC SFC HEATING AND WEAK MOIST ADVECTION-- WITH 60S TO 70 F SFC DEW POINTS -- SHOULD COUNTERACT WEAK LAPSE RATES ALOFT ENOUGH TO RAISE SFC-BASED BUOYANCY TO 500-1000 J/KG RANGE. SEASONALLY STRONG MID-UPPER LEVEL WIND FIELDS -- I.E. 35-45 KT AT 500 MB AND 70-90 KT AT 250 MB -- SHOULD ENHANCE DEEP-LAYER SHEAR ENOUGH TO SUPPORT SOME ORGANIZED SEVERE POTENTIAL. BOW/LEWP FORMATIONS MAY DEVELOP WITH PRIMARY THREAT BEING DAMAGING
WIND. FCST LOW LEVEL SHEAR ALSO SUPPORT POTENTIAL FOR A FEW
SUPERCELLS. THREAT APPEARS PRIMARILY DIURNAL.

...UPPER MS VALLEY...
INCREASING INSTABILITY AND VERTICAL SHEAR THROUGHOUT DAYLIGHT HOURS WILL SUPPORT POTENTIAL FOR SEVERE TSTMS BY AFTERNOON WITH GREATEST RISK INVOF SFC CYCLONE -- WHERE ISALLOBARIC FORCING WILL KEEP BOUNDARY LAYER FLOW RELATIVELY BACKED. ALTHOUGH CONVERGENCE IS NOT EXPECTED TO BE PARTICULARLY STRONG...WEAK CAPPING AND LIFT NEAR LOW SHOULD CONTRIBUTE TO TSTM GENESIS. STEEP LOW-MIDLEVEL LAPSE RATE WILL SUPPORT 1000-1500 J/KG MLCAPE BY AROUND 30/21Z. DAMAGING GUSTS AND LARGE HAIL ARE POSSIBLE. THREAT HERE ALSO APPEARS STRONGLY TIED TO DIABATIC PROCESSES AND SHOULD DIMINISH AFTER ABOUT 31/03Z...THOUGH A SHORT LINE OF STRONG-SEVERE TSTMS MAY EVOLVE FROM AFTERNOON ACTIVITY AND MOVE EWD ACROSS PORTIONS WI. SEVERE POTENTIAL IS EXPECTED TO DIMINISH SWWD ALONG SFC FRONT AS EVEN WEAKER CONVERGENCE AND SHEAR RESULT IN LESS CONVECTIVE ORGANIZATION.

..EDWARDS/GUYER.. 07/30/2004